When Samsung first announced the Galaxy S5 one of the big software features it touted was Download Booster, a feature that uses both Wi-Fi and LTE to make downloading files faster, but as with so many things, most U.S. carriers block the feature on their versions of the phone.
AT&T, Sprint, and Verizon all block the Download Booster on their models of the Galaxy S5. T-Mobile is the only big four carrier that supports the feature. U.S. Cellular also allows the feature, for those who live in the regional carrier’s service area.
Presumably the feature is turned off so it doesn’t put a strain on LTE networks. Verizon doesn’t give a reason as to why it blocks the feature on the Galaxy S5, but does confirm it’s “not currently supported” in the Q&A section of its product page. For its part, Sprint omitted any mention of the feature from its user manual for the Galaxy S5.
Unfortunately, it isn’t the least bit surprising that carriers have blocked the feature. U.S. carriers have a history of blocking features in smartphones. AT&T notably blocked FaceTime over cellular on the iPhone 4S, and later blocked video chat in Hangouts for Android, though it reversed course on both over time.
There’s an argument to be made that the feature was turned off so users don’t accidentally use too much of their limited data plans. There are ways around that by making the feature opt-in, or warning users about it, but three of the major carriers chose to just remove it instead.